1. Field of the Invention
This invention relates to a misfire detector device for use in an internal combustion engine which is conceived on the finding that a sparkplug gap resistance is distinguishable the case in which a spark ignites an air-fuel mixture gas from the case in which the spark fails to ignite the air-fuel mixture gas injected in a cylinder of the internal combustion engine.
2. Description of Prior Art
With the demand of purifying emissions and enhancing fuel efficiency of internal combustion engines, it has been necessary to detect firing condition in each cylinder of the internal combustion engine so as to protect the internal combustion engine against any type of misfire. In order to detect the firing condition in each of the cylinders, an optical sensor has been installed within the cylinders. Further, a pressure-sensitive element has been attached to a seat pad of the spark plug, or the ion current due to an ignition circuit has been measured.
However, it is troublesome and time-consuming to install the optical sensor to each of the cylinders, thus increasing the installation cost, and at the same time, taking much time in carrying out periodic checks and maintenance. In addition, a high voltage withstanding diode is needed to introduce the ion current to a secondary circuit.
Therefore, it is an object of the invention to provide a misfire detector device for use in internal combustion engine which is capable of precisely detecting a misfire by checking a sparkplug voltage waveform applied to the spark plug installed to each cylinder of the internal combustion engine. A further object is to provide such a device-with a relatively simple structure, and which is easy to install and maintain.